<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>10_margin_盒子的外边距</title>
    <style>
        div {
            width: 400px;
            height: 400px;
            margin-left: 10px;
            margin-right: 20px;
            margin-top: 30px;
            margin-bottom: 40px;
            background-color: skyblue;
            

        }
    </style>
</head>
<body>
    <div>你好啊</div>
</body>
</html>